Every item in Podio has its own activity stream, allowing you to easily keep track of what has been changed in your items, and by whom.
You'll find the item activity on the right side when viewing any item. By default you will see all activity, but you can click "Comments" to only show the comments made to the item.
You can also revert any unwanted changes from here. Click on any revision that you'd like to revert. From there you can see what specifically was changed, and you can click the green button to revert the change.
This can be valuable for tracking different stages of processes, or for anytime you need to roll back changes if mistakes are made.
Similar to this is file versioning, which allows you to view and revert changes made to files attached to your apps.